Although the Philippine police chief found no terrorist tie, the SITE Intelligence group, a U.S.-based group that tracks extremist groups, said an operative for the Islamic State claimed that the group was responsible for the attack.

Resorts World Manila, which bills itself as the country's largest casino resort, is located in Pasay City, which is part of metropolitan Manila.

The incident erupted at a time of unrest by extremist groups elsewhere in the country. On May 23, President Rodrigo Duterte declared martial law in Mindanao to combat what he said was a rebellion by Islamic State radicals in that southern Philippines island.